The distinctive characteristics of these particles should help us find out more about a fundamental force of nature known as the strong force.

Back in 2006, physicists at the BaBar experiment in Stanford University in California spotted an energy peak given off when smashing electrons and positrons together, which might indicate the presence of a particle. A team at the LHC found a similar peak in CERN’s data, and have been trying to pinpoint the cause.

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“Our result shows that the BaBar peak is caused by two new particles,” says Tim Gershon of Warwick University, UK, lead author of the LHC work.

The pair are both mesons, and so contain two quarks – subatomic particles that make up matter and are thought to be indivisible. These quarks are bound together by the strong force.

Quarks come in six different flavours known as up, down, strange, charm, bottom and top, in order from lightest to heaviest. The new particles each contain one charm antiquark and one strange quark.

Quarks also have a property called spin, which can be +1/2 or -1/2. When they come together to form mesons, there is an extra spinning effect due to the exact arrangement of the quarks. This adds to the individual spins to give a “total angular momentum”.

Different quark arrangements can give the same total angular momentum, so a particle’s exact configuration is often ambiguous. However, DS3*(2860)– is a special case&colon; its total angular momentum is three, a value for which there is no ambiguity and so it’s clear how the quarks are arranged. This is the first particle containing a charm quark seen to have such properties.

The unique characteristics of this particle could help us explore the strong force, one of the four fundamental forces along with gravity, electromagnetism and the weak force. This is partly because the calculations involved are more straightforward for heavy quarks than lighter ones.

The unique properties of one of these particles could help us explore the strong force

The LHCb team used a method known as Dalitz plot analysis, which had never before been used on LHC data, to untangle the peak into its two components. This helps separate and visualise the different paths a particle can take as it decays. Now that it has been used successfully on the LHCb dataset, says Gershon, it may be applied to more LHC data.

“This is a lovely piece of experimental physics,” says Robert Jaffe of the Massachusetts Institute of Technology. “The fact that LHCb was able to use Dalitz plot methods is a testimony to the quantity and high quality of the data they have accumulated. We can look forward to other similar discoveries in the future.”

This article appeared in print under the headline “New strange and charming particles”